Protein disulfide isomerase inhibitors according to formula I are described, wherein R1 is an aryl or cycloalkyl group, R2 is selected from the group consisting of CN, SO2CH3, NO2, CO2R3, CONHR3, NMe2, and CF3, R3 is selected from H or lower alkyl, R4 is H, halogen, CN, or COOH, and X and Y are C&mdashH or heteroatoms selected from the group consisting of N, O, and S. The protein disulfide isomerase inhibitors can be used for the treatment of cancer in a subject.